Methods and systems for gas well deliquification

ABSTRACT

Methods and systems for deliquification of fluid loaded, packed wells with sub-surface safety valves (“SSSVs”) utilizing timed and tailored chemical treatments. A flow meter measures the flow rate of the well and an intermitter initiates shut in of the well when a particular flow rate is reached. A chemical treatment is applied and allowed to penetrate the length of the well before production is restarted. Predetermined combinations of chemical treatments and production cycles are utilized based on past experience and well data, and the entire process can be automated through the use of a computer system.

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 60/854,481, filed on Oct. 26, 2006, entitled METHODS ANDSYSTEMS FOR GAS WELL DELIQUIFICATION, the entire content of which ishereby incorporated by reference.

BACKGROUND

This invention pertains to the deliquification of gas wells, andparticularly to methods and systems for deliquification of fluid loaded,packed wells with sub-surface safety valves (“SSSVs”) utilizing timedand tailored foamer treatments with cyclical, repeating sequences ofshutin, batch and fall applications, and flow back.

The accumulation of water and liquid hydrocarbons in well bores is aproblem both in natural-gas production and underground gas storage.Siphons and accompanying equipment, such as gas-lift valves and timingdevices, probably are the most logical choices to relieve this problemwhere water production is profuse. However, such systems are expensiveand often are not justified for marginal wells or those that produceonly a little water. The number of such wells is large and is increasingrapidly, particularly in underground gas-storage projects where wateraccumulates only after extended withdrawal periods and only to a limitedextent. Although bailing and swabbing usually will remove the liquidsfrom such wells, these practices are relatively expensive and timeconsuming.

There are many other approaches to the deliquification of gas wells.These approaches include: velocity strings, plunger lift, pump jacks,compression. submersible pumps, foaming and swabbing. Each of thesetechnologies has applications in which they perform best. For instance,high gas to liquid ratio wells with high well pressure are well-suitedfor plunger lift applications. Also, high water flow rates are wellsuited for submersible pump applications.

A widespread method for removing water from well bores is the use offoaming agents. The method is rapid, relatively inexpensive, andgenerally more cost effective. Furthermore, only a lubricator or smallpump is required for the treatment. Foaming agents form a light foamcolumn when properly mixed with the water or brine in the well bore andagitated by even a small amount of gas from the formation. Thislightened column is lifted from the well by gas pressure that is too lowto lift a column of water. Furthermore, the foam is rigid and, bycapturing gas in the form of small bubbles, prevents the gas frombypassing water in large casings.

A subsurface safety valve (“SSSV”) is a safety device installed in awell below the wellhead with the design function to prevent uncontrolledwell flow when actuated. These devices can be installed and retired bywireline and/or pump down methods or be an integral part of the tubing.Most offshore gas wells that are loaded with SSSVs are presumed to needa capillary string that will extend below the SSSV to inject foamer tomaintain gas well unloading. That type of capillary string technology isvery expensive. The total cost is perhaps in the range of $100,000 to$200,000 per well. The use of capillary string technology in conjunctionwith SSSVs is complicated, and therefore expensive, because running acapillary string through the length of the tubing interferes with theability to shut the SSSVs. Instead, the capillary tubing has to bemodified to provide for retractable sections that bridge the SSSVs andcan be mechanically retracted when the SSSVs need to be shut.

Another option for deliquification of gas wells having SSSVs is the useof foam sticks. First, the well must be shut in. Then a foam stick hasto be physically dropped through the length of the tubing with the SSSVsopen. Materials in the foam stick then act to create foam which can beremoved from the well. The use of foam sticks is very labor intensiveand therefore undesirable.

What is needed, therefore, is a method for deliquifying gas wells loadedwith SSSVs that is low in cost and risk.

The present invention relates generally to the field of gas and oilwells. In particular, this invention pertains to methods and systems forremoving liquid from gas wells using repeated and cyclical sequences ofshutin, batch and fall foamer application, and flow back.

Generally, the current invention pertains to a method fordeliquification of fluid loaded, packed gas wells with SSSVs. The methodutilizes shut in and production intervals. Production cycles follow theshut in cycles during the unloading phase. Once the unloading phase endsand normal production begins, the same method can be followed to tailortreatment cycles to maintain optimum production.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a general schematic of a gas well deliquification system;and

FIG. 2 shows a graph comparing how a gas well could perform duringsingle batch treatments vs. cyclical batch treatments.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to a method for the deliquification of gaswells. In particular, the method involves the timed application offoamer treatments during sequential shut in cycles. The gas well can bemodified with a flow meter and an intermitter to control the shut in andproduction cycles.

One aspect of the present invention is the use of a flow meter orpressure monitor and an intermitter in the deliquification of a gaswell. A flow meter measures any kind of liquid that is preset by theuser. With appropriate flow controlling software that is commerciallyavailable and sold in conjunction with the flow meter, the flow metercan be used to monitor the gas flow in a gas well. Some commerciallyavailable flow meters include TOTALFLOW EFMs (ABB, Zurich, Switzerland).Preferably, the flow meter and associated software is configured toregister a selected flow rate or pressure of gas, such as the minimumflow rate or pressure that is allowed before the need for adeliquification treatment. Once this particular flow rate or pressure ismeasured by the flow meter or pressure monitor, a signal is sent to theintermitter. An intermitter is a manual or automated flowline valvecontrol with appropriate safety controls to allow for automated shut inand restart. Some commercially available intermitters include those madeby Ferguson Beauregard (Tyler, Tex.). Once the signal is received, basedon the flow rate or pressure measured by the flow meter or pressuremonitor, the intermitter then shuts in the gas well for deliquificationtreatment.

An additional aspect of the present invention is a method for thedeliquification of gas wells that have been shut in through the use of aflow meter and intermitter. Preferably, a chemical treatment is appliedto the shut in well and allowed to penetrate the length of the tubing.The chemical treatment can be stored in a tank having a pump and a tubethat travels to an injection point at the wellhead. When the pump isengaged at the appropriate time, subsequent to shut in of the well, thechemical treatment is applied to the fluid in the well. The shut ininterval should last long enough for the chemical treatment to penetratethe entire fluid level. For example, a fall rate of 2000 ft/hr should betaken into consideration. If the well is 10,000 feet deep, then it mustbe shut in for 5 hours to allow the chemical treatment to penetrate.Weighted foamers are also useable with this method to allow fasterpenetration once the foamer gets to the fluid level.

Preferably, the same software and computer system that measures the flowrate of the well and engages the intermitter to shut in the well alsocontrols the pump and the chemical treatment. In that way, the entiredeliquification process can be carried out simultaneously using onesystem. When the appropriate flow rate is measured, the intermitter isengaged to shut in the well, and the appropriate amount of a chemicaltreatment is applied to the well. After a preset period of time, whichallows the chemical treatment to take affect, the intermitter is againengaged by the computer system and software to open the well again.

A further aspect of the present invention is the selection of anappropriate chemical treatment to use for deliquification while the wellis shut in. An appropriate foamer must be selected. Suitable foamersinclude non-ionic, anionic, cationic, amphoteric, and other chemicalfoamers, or mixtures thereof. Some foamers are available with additionalcomponents, such as scale inhibitors and corrosion inhibitors. Anappropriate foamer can be selected according to individual preferenceand personal experience. Commercially available foamers include thosemade by MultiChem Group, LLC (Sonora, Tex.).

Preferably, the flowmeter and intermitter are used to tailor the shutin/treatment and production intervals to maximize gas productionoverall. While the well is shut in and is undergoing treatment, it isnot producing gas. However, the deliquification treatments during thisunloading phase are necessary to maintain a productive flow of gas.Ideally, a series of different interval schemes are utilized and testedto determine which results in maximum production over time. Each wellwill react differently depending on the amount of water present and theflow rate, so one specific interval scheme cannot be adopted for everycase. Anyone of skill in the field is capable of varying the treatmentintervals and monitoring the results in order to determine a scheme thatis ideal for a particular well. In some cases, these different treatmentschemes can be done manually until the ideal settings are worked out.Then the system for deliquification utilizing the software, theintermitter, and the chemical pump can be configured to apply theseideal settings automatically. In some cases, the first unloadingtreatment may bring the well to the normal production cycle, whereas insome cases the unloading cycle will take multiple treatments.

In an optional step, during the shut in interval, the well can also bepressurized with high pressure gas, such as methane, compressed or solidcarbon dioxide, or nitrogen gas. Pressurization of the well results inthe dissolving of both the methane gas and the pressurized gas in water.Preferably, the pressurized gas is carbon dioxide because it has moresolubility in water. Nitrogen gas is also usable. Although compressedair could be utilized, the corrosiveness of oxygen makes it less thanideal. The production of foam in the shut in well is increased byinjecting the pressurized gas into the well. The use of pressurized gasin conjunction with the shut in/treatment cycle is typically used with“dead wells,” or wells that have become so loaded with water that theyare no longer producing a significant amount of gas, or any gas at all.

FIG. 1 shows a general schematic of how the gas well deliquificationsystem 10 could work in conjunction with a gas well 20 having at leastone sub surface safety valve (“SSSV”) 25. An output line 30 of the gaswell 20 is equipped with a gas pressurizing stub 32, a flow meter 34,and an intermitter 36. A chemical pump 42 works in conjunction with theintermitter 36 to inject an appropriate chemical treatment into the gaswell 20 after shut in is initiated by the intermitter 36. Theintermitter 36 can use a flowline valve control 44 to allow theautomated shut in and restart of the gas well 20. The gas flowmonitoring software and hardware 46 works in conjunction with the flowmeter 34 to measure the gas flow rate and determine when shut in of thegas well 20 should be initiated. Optionally, the gas pressurizing stub32 also injects pressurized gas during shut in of the well. Thisinjection of pressurized gas can be carried out in conjunction with aninlet valving system 48 having appropriate safety controls.

Example 1

FIG. 2 shows a graph comparing how a gas well could perform duringsingle batch treatments versus cyclical batch treatments. During thefirst couple of weeks of gas production, at the left of the graph, thegas well has first been unloaded using single batch treatments. Thesesingle batch treatments could be single foam sticks or single batches ofliquid foamer that are applied to the well without retreating it. Singletreatments such as these remove large batches of water and result in thesharp peaks that are visible at the left side of the graph. Once thecyclical treatment begins, there are initially some large peaks, buteventually only small amounts of water are being removed each time.Thus, the graph levels out and becomes more cyclical.

1. A method for deliquification of a gas well having subsurface safetyvalves (“SSSVs”), comprising: measuring a gas flow rate of the gas wellto determine when a predetermined minimum gas flow rate is reached;shutting in the gas well with an intermitter after the predeterminedminimum gas flow rate is reached; applying a chemical treatment to thegas well with a chemical pump; waiting a predetermined amount of time toallow the chemical treatment to penetrate the gas well; and activatingthe gas well with the intermitter after the predetermined amount oftime.
 2. The method of claim 1, wherein the steps are carried outautomatically through the use of a computer system.
 3. The method ofclaim 1, wherein the chemical treatment comprises one or more foamers.4. The method of claim 1, wherein the chemical treatment comprisesnon-ionic foamers, anionic foamers, cationic foamers, amphotericfoamers, or mixtures thereof.
 5. The method of claim 1, furthercomprising, after the step of applying a chemical treatment, injectingpressurized gas in to the gas well with a gas pressurizing stub.
 6. Themethod of claim 5, wherein the pressurized gas is methane, compressed orsolid carbon dioxide, or nitrogen gas.
 7. The method of claim 1, whereinthe steps are repeated in a cyclical fashion to optimize production ofthe gas well.
 8. The method of claim 1, wherein the predetermined amountof time is equal to approximately one hour for every 2000 feet of welldepth.
 9. A method for deliquification of a gas well having subsurfacesafety valves (“SSSVs”), comprising: measuring a gas flow rate of thegas well to determine when a predetermined minimum gas flow rate isreached; shutting in the gas well with an intermitter after thepredetermined minimum gas flow rate is reached; applying a foamer to thegas well with a chemical pump; injecting pressurized gas in to the gaswell with a gas pressurizing stub; waiting a predetermined amount oftime to allow the foamer to penetrate the gas well; and activating thegas well with the intermitter after the predetermined amount of time.10. The method of claim 9, wherein the steps are carried outautomatically through the use of a computer system.
 11. The method ofclaim 9, wherein the chemical treatment comprises one or more foamers.12. The method of claim 9, wherein the chemical treatment comprisesnon-ionic foamers, anionic foamers, cationic foamers, amphotericfoamers, or mixtures thereof.
 13. The method of claim 9, wherein thepressurized gas is methane, compressed or solid carbon dioxide, ornitrogen gas.
 14. The method of claim 9, wherein the pressurized gas isinjected into the gas well using a gas pressurizing stub.
 15. The methodof claim 9, wherein the steps are repeated in a cyclical fashion tooptimize production of the gas well.
 16. The method of claim 9, whereinthe predetermined amount of time is equal to approximately one hour forevery 2000 feet of well depth.
 17. A method for deliquification of a gaswell having subsurface safety valves (“SSSVs”), comprising: measuring agas flow rate of the gas well to determine when a predetermined minimumgas flow rate is reached; shutting in the gas well with an intermitterafter the predetermined minimum gas flow rate is reached; applying achemical treatment to the gas well with a chemical pump; injectingpressurized gas in to the gas well with a gas pressurizing stub; waitinga predetermined amount of time to allow the foamer to penetrate the gaswell; activating the gas well with the intermitter after thepredetermined amount of time; and repeating the steps in a cyclicalfashion to optimize production of the gas well, wherein the steps arecarried out automatically through the use of a computer system.
 18. Themethod of claim 17, wherein the chemical treatment comprises one or morefoamers.
 19. The method of claim 17, wherein the chemical treatmentcomprises non-ionic foamers, anionic foamers, cationic foamers,amphoteric foamers, or mixtures thereof.
 20. The method of claim 17,wherein the pressurized gas is injected into the gas well using a gaspressurizing stub.
 21. The method of claim 17, wherein the pressurizedgas is methane, compressed or solid carbon dioxide, or nitrogen gas. 22.The method of claim 17, wherein the steps are repeated in a cyclicalfashion to optimize production of the gas well.
 23. The method of claim17, wherein the predetermined amount of time is equal to approximatelyone hour for every 2000 feet of well depth.